Inspecting instrument.



-| STATES PATENT OF ICE;

OSCAR F. TALLMAN, OF ST.- LOUIS, MISSOURI, ASSIGNOR, BY MESNE ASSIGNMENTS, TO

W. N. MATTHEWS AND BIIEtO'lIlFIEIR- INCOIRCIEORATIEID, OF ST. LOUIS, MISSOURI, A COR- POBATION OF NEW MEXICO.

To all wig/0m may concern:

Be it known that I, OSCAR F. TALLMAN, a.

citizen of the United States, residing at the city of SteLouis, State of Missouri, have invented a certain new and useful Improve-- ment in Inspecting Instruments of which the following is a full, clear, and exact description, such as will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawings, forming part of this specification, in which Figure 1 is a diagram illustrating the constructlon of my improved inspecting instrument and a method of its use. Fig. 2 is a a diagrammatic illustration of the manner in v cable conductors, for the purpose of detecteating such a fault in a hidden conductor ing faults therein, such as may; be caused by short-circuiting, grounding or the presence of wet spots in-the cable. It will be understood that the'usual method employed in 10- consists in impressing upon the conductor whlch 1s m trouble, some form of an lnterruptedor alternating current of arform differing from the currents to be'found in t e associated conductors, and then in exp oring the cable with some form of detecting instrument. The detecting instrument is influenced\by the magnetic field which is in- 351 \duced aboutihe cable by the presence of the current impr ssed on the conductor, in some fashion such that the presence of such magnetic field may be ascertained by the inspector. It is desirable to keep this test our rent at as low a value as possible in order to prevent itsinfluen'cing the lines which are 1 associated with the line under test, as when the test current is of suflicient quantity to affect such other lines, the telephones on such other lines "are rendered noisy and the service interfered with. This necessitates the inspecting instruments being capable of detecting a test current of small quantity.

Furthermore, the inspecting instrument must be readily responsive to the characteristic variations of, the test current in order that the inspector may distinguish it from the other electrical. disturbancesjwhich are constantly present inthe cable.

Specification of Letters Patent.

illustrated in-Fig. 2. a are connected with the terminals offthecoil 'the'wire :4; a

' msrnc'rme INSTRUMENT.

Patented Mar. 7 1916.

Application filed April 11 1914. Serial No. 831,256.

It is the purpose of my invention, there-- fore, to provide an improved form of inspecting instrument which is possessed of a high degree of sensitiveness and responsiveness.

It is likewise an object of my inventionto produce such an' inspecting instrument- With these and other objects in view, which will be obvious or hereinafter point- 4 ed out, 1t will be understood by reference'to the accompanying drawings that my invention includes a laminated core member 1 z a v.

1 which preferably, is composed of a bunch of soft iron wires; This core is wound with a" it duplex wmdmg composed of a wire, 2 for1'ning a portion of what I shall termthe re-- ceiver circuit, and a wire 4 forming a portion of whatI shallterm the condenser cir- 5 cuit.- These wires are wound on'the core-together, and are transposed across each-other as diagrammatically at suitable intervals,

The ends of thejwire 2' 5"of a polarized telephone receiver, whereby aiclosed circuit .is formedthrough said coil 15 and about the core 1. -Ar'zondense'r 6 is placed in series For the purpose of' illustrating the'operation of'the device, let 7 represent a telephone cable containing the conductors 8, one of which 9 is--short-circuited with the cable sheath at some unknown point'X.

- Let 10 represent any suitable-meanslof I current supply, one pole of which may be connected to the cable sheath and the. other pole of which is adapted to conductor 9 by some suitable: interrupting ductor 9 to the unknown point-of fault at X,

from which point it WiILreturn 'along the cable sheath. This will produee'a mag netic (field about the cableas far as the fault,

but no farther, which field will have the par-- -ticular characteristic produced bythe test I thrown into and out of-.electr1cal connection with; the

1 in the winding formed bycurrent will'be impressed on the-conductor v 9, wh1ch-current will continuealong the concurrent. -When the wound core of the testing instrument is brought within th1s field,

an E. M. F. and Current will be inducedin the receiver circuit and the condenser circuit by the transformer action of'the field upon the core 1 and the windings. thereon.-

While this current and E. F. are present in winding 2, the permanent magnet of. the telephone receiver will be denergi'zed' by coil5, permitting the diaphragm to move. When thecoils oni the receiver'magnet are then deenergized,

away from the magnet.

the diaphragm of thereceiver is attracted by the permanent magnet of'the receiver. Thus, the diaphragm is caused to vibrate by the alternate energization and deenergiza tion of'the coils on the telephone receiver magnet. This is, ofc'ourse, the well known I the magnet and diaphragm. of the telephone receiver. Such influences, oficourse, are the resistance, the capacity, and the inductance of the windings 2 and 5. Moreover, the

core 1, when energized the field about the cable, tends to retain-its magnetism. toa greater or less degree after the current in the conductor 9 has beeninterrupted. The action of core 1, therefore,-in thisparticular upon the coil 2 is to prolong-and attemuate the energization'of the telephone receiver coils. and. coil 2 is that of an impedance coil. This impedance, artificially produced in the receiver coil 5 by core 1, if not counter-- acted, would act in the usual fashion to pre-" vent immediate denergization of: said coil.

5. Hence the diaphragm would not be subected to the sharply contrastin influences of repulsion and attraction whic are necessary to make known to the ear of the operator the presence of the characteristic field about the cable 7., Therefore, the instrument would not have the proper sensitiveness. By the addition of the condenser circuit 4, however, the impeding influence of coil 1 is opposed and counteracted. When current is present in the conductor 9 and the resulting field in existence about the cable 7 "a current and E. M. F. will be in-.

duced in the winding 4 as in the winding 2. This will operate to charge the condenser 6.

Immediately uponthe interruption of the current in conductor 9, the condenser 6 will discharge back over the winding 4 in the opposite direction. This will havethe'effect of damping out of core 1 the residualmagnetism which tends to maintain the current in the winding 2-in the original direction. Consequently, the current is per-' In-this the action of core 1 in the mittedto reverse in the receiver coil 5' mediately-when the current on conductor 9 is interrupted. Although I the improved results obtainable with my device are secured, it will be understood that I am not limited to the particular theory of operation.

ment in'a device of this kind, however, is not eifective, for the reason that the condenser increases the capacity of the circuit to suchan extent that the effectiveness of the induced-current and E. M. F. in the telephone receiver circuit is greatly reduced and consequently, the receiver isnot sufficiently sensitive or. responsive.

Asabove stated, the wires 2 and 4 are transposed, at suitable intervals,. whereby any inductive effect of one upon the other is prevented It is [obvious that the 'deviceis equally suited for-the location of wet spots or other faultsby which the conductor is grounded, as indicated" at-.Y, likewise, where two conductors are'crossed in the cable in which r ca'sethepoles of the current producing deiviceaiconnected on the crossed conductors. "It is obvious 'also that my improvement may benernployed in all similar uses wherein a sensitive-detectinginstrument is required.

1 The "inspecting instrument above described mla'y be embodied in-.a .very compact commercialform which can be easily carried pocket of the inspector. By virtue of its'simplicity, it is adapted to withstand rough usage, and is constantly ready for use, as no adjustments of any kind are required to operate the same, 7

Ilaving tli described the construction of myimprovedinspecting instrument, and what I-believe; to be the theoryof its operation, I am aware that various changes and In some instances, it has been customary ;:in various devices to insert, a condenser across the energizing circuit of an electroi magnet to counteract the impedance and inductance of the'circuit. Such an arrange-- believe the foregoing to be a proper explanation of the action whereby modifications therein may be made without departing rom the scope of what I claim to be my invention.

What I claim is: 1. An inspecting instrument. comprising a core membersupplied' with ,a winding having included in circuit therewith the coils of .a telephone receiver, and a second windng-woundon sald core with the said windmg and having a condenser included in series .therewith; said windings being disposed'in similar inductive relationship to saidcore. l

2. Ar -inspecting instrument comprising a core member supplied with a winding, an

electromagnetic indicating device having its coils included in circuit with said winding', saidcore-being provided with a second windmg-havmga condenser ncluded 1n series therewith; both of said circuits being in the nature of secondary circuits.

3. An inspecting instrument comprising a portable core member provided with inde pendent windings disposed in similar inductive relationship thereto, one of said windings having connection with an indicating device, and the other of said windings forming part of an induction circuit closed upon ltself through a condenser.

4. In an inspecting device, a movable core member, an indicating device, a winding disposed in inductive relationship with the core member'and in operative relationship with the indicating device, and a condenser circuit including a condenser and a coil disposed in inductive relationship with the core member; the construction and arrangement of parts beingsuch that the pressure in theincreased as the intencondenser circuit is sity in the winding is increased.

5. An instrument of the sort described vice, and the other com risin an indicatin device a c.0ng secondary inductive relationship a' pair of separate circuits, one of which is arranged in operative relationship to the indicating dethrough the condenser.

6. In a device of indicating device, a condenser, cally susceptiblecore member, a, w1nding operativelyassociated with the indicating device and arranged for secondary cooperation with the core,- and a second winding a magnetiarranged for secondary cooperation with the V core member and closed through the condenser.

In testimony whereof I hereunto aflix my signature in the presence .of two witnesses, this 23d day of March, 1914.

- --1 OSCAR F. .TA Witnesses:

M. B. SMITH, C. S. 'BU'I ER.

of which is closedthesort described, an I 

